Data between the lowest resolution reflection and 15 E will be collected from single crystals of a variety of icosahedral virus particles and virus-like particles generated in coat protein expression systems and a modified low angle scattering camera. The data will be used to generate 3D structures at 20 E resolution using icosahedral harmonic analysis. The structures will be used for three purposes. 1. For comparison with previously determined, comparable resolution, structures generate with image analysis of cryo electron microscopy data with the goal to establish the quality of the contrast transfer function corrections applied to the EM data. 2. Use the x-ray derived structures for phase extension to 15 E resolution or higher to see if the low resolution x-ray data solves the phase problem for virus crystallography. 3. Examine the RNA or DNA density distribution in all the viruses for evidence of icosahedral symmetry and for the influence of different charge neutralizing strategies on its organization.